xi ANCESTRY OF CAMELS 289 period, and for a long time after, there were no types referable to the Camelidae in the Old World. Though a Camel in many features of its organisation, Poebrotheriutn was " generalised " in many ways. Thus the metacarpals and metatarsals were not fused to form a cannon bone, and the two lateral digits were represented by splint rudiments of metacarpals and meta- tarsals. The dentition was complete. The skull though distinctly Tylopodan, also shows more generalised characters. Thus the .orbit is not quite, though nearly, completed by bone. In the Camel it is quite closed. The nasal bones are much longer, reaching nearly to the end of the snout. The odontoid process of the axis vertebra is not spout-like as in existing forms, but cylindrical, though slightly flattened upon the upper surface. The scapula is described as being more like that of the Lama than of the Camel, though variations occur which approxi- mate to the CameL The brain, judging of course from casts, has those sulci " which are common to the whole series of Ungulates, and closely resemble those of a foetal Sheep." FlG ^sT^A^rioTTTrface of Later in historical sequence than axis of Bed Deer. xf. 0, Poebrotherium, and structurally inter- tericn^zygniSphySs*; «S fora- mediate between it and Protolabis,, IS »ue» for second spinal nerve, .,-,.-. ,~ -T ,7 -r* (From "Flower's Qst eulogy.) the Miocene genus Gomphothervu.wi. It VJ shows an advance in structure upon PQebrotJierium, in that the orbit is completely encircled by bone, though the posterior wall is thin; jhe lower canines instead of being incisiforxn are curved back as in later Camels, and separated by a wide diastema from the preceding and the succeeding teeth. Later in age than PoebrotJierium is Protolabis, a Tylopod in which the full number of teeth is still retained ; its skull presents no particular changes from the Poebrotherine type; the nasals, however, are somewhat shortened. Later still in point of time is P1rocamelii<8. In this form we have apparently an ancestral stock, whence both Camels and Lamas were derived. The upper incisors are as in existing forms, but the first and- second persist for a somewhat longer time. The skull shows two well-marked types of structure; in P. oecidentalis TO!,. X "O"